This invention relates generally to optically-based methods and apparatus for identifying articles and, specifically, to methods and apparatus for identifying optically coded articles.
In U.S. Pat. No.: 5,448,582, a multi-phase gain medium is disclosed as having an emission phase (such as dye molecules) and a scattering phase (such as TiO2). A third, matrix phase may also be provided in some embodiments. Suitable materials for the matrix phase include solvents, glasses and polymers. The gain medium is shown to provide a laser-like spectral linewidth collapse above a certain pump pulse energy. The gain medium is disclosed to be suitable for encoding objects with multiple-wavelength codes, and to be suitable for use with a number of substrate materials, including polymers and textiles.
A class of industrial problems exist in which a large number of items must be separated, identified, counted and/or sorted. Present day methods cover a broad spectrum of solutions. One solution applicable to macroscopic and visually identifiable items involves a manual process wherein workers sequentially select items from among many items in a group by identifying an intrinsic characteristic of an item or by a visually-readable coding system that is incorporated into the item. Once selected, the items are directed, either manually or by use of a conveyance, to a location where items possessing a common attribute are stored or further processed. In cases where inventory control is of interest, the selected items can be counted and tabulated either manually by some direct action by a worker or automatically as the selected item passes through a counting device.
In the commercial laundry industry, for example, rental garments are returned in unsorted groups and washed. Workers select single garments, place the garments on a hanger and subsequently onto a conveyor which deposits the garments into one of several holding areas. An appropriate one of the several holding areas is chosen for an individual garment based on a man-readable code applied onto the garment, usually inside the collar, which identifies some attribute common to all garments in a holding location. Typically, attributes include, for example, a day of the week, a route number, or an end user name. Similarly, in the linen supply industry, linens are delivered to a laundry in large, unsorted groups. Workers select individual linen items from a group and identify each item by a characteristics thereof, for example, color, shape and/or size. The selected and identified item is then directed to an appropriate area for washing by a specific wash formulation.
As can be appreciated, the manual labor to identify, count, sort and tabulate items (e.g., linen and/or garment items) has numerous limitations. A limitation in processing throughput is of particular interest herein. In some laundries about 100,000 or more individual items must be processed in a single 8-hour work shift. Since workers are required to perform multiple tasks on each item (e.g., identify, count and sort each item), only a limited number of items can be processed by a typical worker in an 8-hour shift. Further, the burden of manually performing multiple tasks on each item may also lead to inaccuracies in the identifying, sorting and counting processes.
In an effort to eliminate, or at least to minimize, the limitations in the manual processes outlined above, automated solutions have been sought. Conventional automated processes have been developed to improve the accuracy of and to minimize the labor required to identify, count and sort individual items. For example, bar code labels (typically interleaved 2 of 5 symbology) and Radio Frequency (RF) chips have been employed by laundries to achieve these results. These techniques, however, do have limited longevity particularly since the labels and chips are exposed to the harsh industrial laundry environment. Additionally, a solution which employs the bar coded labels suffers for it is time consuming and, at times, extremely difficult to locate a label on a large item when the label is not properly aligned with, i.e. in a field of view of, the bar code reading device. While RF chips do not suffer from the alignment problem, RF chips are troublesome due to their unproven longevity and high costs.
In U.S. Pat. No.: 5,881,886, issued Mar. 16, 1999 an alternate method of identifying items is disclosed. In this alternate method, photonically active materials, such as patches, labels and threads, can be affixed to garments and linens. A suitable selection of the materials each having, for example, a distinct and uniquely identifiable narrow-band lasing emission are utilized to form optically identifiable codes. The codes permit the identification of the garments, linens and other articles. In one embodiment, two or more fibers or threads, herein after referred to as LaserThread(trademark), exhibit detectable emissions that are incorporated into the garments, linens and other articles to optically encode information into these articles. For example, LaserThread(trademark) may be incorporated into garment labels for uniquely identifying a rental garment, or characteristics thereof, during processing. Similarly, LaserThread(trademark) may be sewn into borders of linens, e.g., into the hem of a table linen, for uniquely identifying linens and/or characteristics thereof. As is noted in this U.S. Patent, LaserThread(trademark) emits laser-like emissions when excited with, for example, a laser having specific wavelength, pulse energy and pulse duration. Generally, the required excitation laser has a wavelength in the red to blue region of the visible spectrum and can provide radiant energy densities on the order of, for example, about 10 millijoules per square centimeter when an about 10 nanosecond pulse is directed at the LaserThread(trademark). Exemplary excitation sources include, for example, flashlamp-pumped, Q-switched, frequency doubled Nd:YAG lasers, diode-pumped, pumped Q-switched, frequency-doubled Nd:YAG lasers, and sources derived from other nonlinear products involving principally Nd:YAG lasers or other laser crystals.
However, commercially available excitation sources suitable to excite photonically active materials such as, for example, LaserThread(trademark), can be costly. Therefore, it can be appreciated that an identification system design which maximizes the efficiency of excitation pulse energy is important. It can further be appreciated that the efficiency of excitation pulse energy can be maximized by tightly controlling the location and orientation of photonically active materials incorporated within an article to be evaluated. If tight controls are maintained, then a narrow excitation beam of fixed orientation can impinge on the photonically active materials incorporated within the article to be evaluated with a predictable degree of certainty. Alternatively, if the controls of the location and orientation of the photonically active materials are relaxed, then a targeting system is needed to locate the photonically active materials incorporated into the articles such that an excitation beam can be directed to excite the materials.
As was discussed above, the ability to tightly control the orientation of photonically active materials incorporated within an article under evaluation is particularly troublesome during various processing operations. For example, a region of the article containing the material may be soiled or otherwise obstructed and, thus, the irradiation of the photonically active materials is prevented. Therefore, the inventor has realized that it is advantageous to employ a targeting system and an identification system with processes for separating, identifying, counting, optionally sorting and authenticating and validating the authenticity of articles.
The foregoing and other problems are overcome and the objects and advantages are realized by methods and apparatus in accordance with embodiments of this invention.
In a preferred, but not limiting embodiment the articles being examined are banknotes and similar basically flat items, and these teachings are employed during the processing of banknotes, such as the validation and authenticity checking of banknotes and other items containing at least one security feature.
A method and a system are disclosed for processing a banknote. The method includes providing a banknote having at least one photonically active security feature, the banknote being moved along a conveyance path; illuminating the at least one security feature with light from a stimulus source; identifying a location of the at least one security feature by detecting an emission from the security feature; directing an excitation source at the identified location; illuminating the at least security feature with light from the excitation source; and detecting a further emission from the photonically active security feature in response to the light from the excitation source.
The step of identifying may include operating a linescan camera having scan axis that is parallel to a conveyance axis, or operating a linescan camera having scan axis that is perpendicular to the conveyance axis. The step of identifying may also include operating a single element detector to accumulate a line scan along the banknote at a same cross-axis location as a field of view of the excitation source.
In one embodiment the step of directing includes delaying operation of the excitation source for a period of time that is a function of at least a speed of conveyance, and a distance between a illumination points of the stimulus source and the excitation source.
The photonically active security feature can include at least one thread or planchette or other structure, such as a tape, having a substrate material and an electromagnetic radiation emitting and amplifying material for providing a laser-like emission. The structure can be embedded within or disposed on the banknote. The detected further emission may be an optical code for identifying at least one characteristic of the banknote.